75 Integrating Membrane Transport with Male Gametophyte ... - TAIR

155 Dissecting genetic pathways underlying floral organ abscission
Michael Lewis, Michelle Leslie, Sarah Liljegren
UNC-Chapel Hill
We are using Arabidopsis as a model to study cell separation by focusing on the controlled shedding, or abscission, of
floral organs after fertilization. Our lab has identified NEVERSHED (NEV) as a gene that is required for the abscission of
sepals, petals and stamens. The cellular morphology of nev mutant flowers and activity of the NEV gene product suggest
that it plays a role in vesicle trafficking. To identify factors that may physically interact with or downstream of NEV, we
have conducted a screen for mutations that restore organ shedding in a nev background. Four recessive mutations have
been isolated that confer nearly wild-type abscission in nev flowers as well as another recessive mutation that shows a
partial rescue. We have also identified four dominant mutations that suppress the nev phenotype, including one which is
intragenic. Characterization of the loci corresponding to these nev suppressors will facilitate further dissection of vesicle
trafficking pathways required for plant cell separation.
156 FOLDED PETALS is involved in petal maturation in Arabidopsis
Noritaka Matsumoto 1 , Seiji Takeda 2 , Kiyotaka Okada 1
1
Department of Botany, Graduate School of Science, Kyoto University, 2 Department of Cell and Developmental
Biology, John Innes Centre
Flower has four types of organs, sepals, petals, stamens, and carpels. Though well-known ABC model is explaining
the mechanism of the decision of the floral organ identity, little is known about the maturation processes of floral organs.
Morphologically, petals have relatively simple structure to other floral organs: matured petals consist of fewer layers of
cells and fewer types of cells. This structural simplicity makes petals a good model system to analyze process of organ
maturation in flower. The morphological aspects of petal maturation in Arabidopsis were described (Smyth et al., 1990),
which contained three major phases. 1) Petal primordia appear between sepal and stamen primordia. 2) Petals elongate
along the inside of sepals through narrow space between the sepal and anther. 3) Petals elongate rapidly to mature when
flower opens. However, molecular and genetical mechanisms controlling these processes are still unclear.
To investigate the mechanism underlying the processes, we screened mutants with defects in petal morphology,
especially in the process of the maturation. We isolated a mutant, folded petals (fop), which petals are folded when
the flower opens. In fop, the position and the identity of floral organs were normal. Histological analysis showed that
the petals started folding around when elongation began (the second phase shown above). The matured petals in fop
showed no significant difference in size and shape from those in wild type, except for the folded form. FOP encodes
a putative transmembrane protein with unknown function. To address the character of FOP protein, we are analyzing
cellular localization of FOP:GFP fusion protein both in transgenic plants and in protoplasts of suspension cells. Analysis
of pFOP:GUS transgenic plants revealed that FOP was expressed not only in petals but also in other floral organs. We
will discuss about the relationship between the function of FOP and the petal maturation.